$OpenBSD: patch-src_ptlib_unix_socket_cxx,v 1.4 2017/05/07 20:48:29 espie Exp $
--- src/ptlib/unix/socket.cxx.orig	Fri Apr 28 01:42:19 2017
+++ src/ptlib/unix/socket.cxx	Fri Apr 28 01:49:44 2017
@@ -67,6 +67,8 @@
 #include <ifaddrs.h>
 #endif
 
+#include <unistd.h>
+
 #if defined(P_FREEBSD) || defined(P_OPENBSD) || defined(P_NETBSD) || defined(P_SOLARIS) || defined(P_MACOSX) || defined(P_MACOS) || defined(P_IRIX) || defined(P_VXWORKS) || defined(P_RTEMS) || defined(P_QNX)
 #define ifr_netmask ifr_addr
 
